The present invention relates to a method of waterproofing a group of wires, such as wires of a wiring harness. The wiring harness may be used in an automotive vehicle and may have a grommet mounted on the group of wires. The invention also relates to an applicator for applying a sealant or other material to the wires.
Many automotive wire assemblies pass through a panel between an engine compartment and a passenger compartment of an automotive vehicle. A tubular rubber grommet often is used in this situation to prevent intrusion of water into the passenger compartment. More particularly, the tubular rubber grommet is fitted in a hole through the panel and the wire assembly is introduced through a hole of the grommet. However, water may flow by capillary action through any clearances that may exist between the respective wires of the wire assembly or between the wires and the grommet.
A sealant has been applied in the clearances inside the grommet to achieve waterproofing between the grommet and the wires of the wire assembly. However, the application of a waterproofing sealant to the wires and the grommet has not been easy.
Another waterproofing method applies a sealant to the respective wires. The wires then are wrapped with a film and are bundled with tape to achieve a circular cross section. The bundled wires then are fitted into the grommet. This method enables the waterproofing sealant to be applied when the wire assembly is manufactured. Accordingly, the waterproofing process can be simplified and speeded up. For example, a plurality of wires for a wire assembly can be arranged in a line. Nozzles are provided at opposite sides of this wire group, and a sealant is discharged simultaneously from the nozzles for application to opposite sides of the wire group (see, for example, Japanese Unexamined Patent Publication No. 10-172360). More particularly, a U-shaped nozzle holder is provided with fixed arms that are spaced apart sufficiently to be disposed on opposite sides of the wire group. The nozzles are mounted in the arms of the U-shaped holder, such that a nozzle in one arm faces a nozzle in the other arm with a fixed spacing between the opposed nozzles. The wires of the wire group are positioned between the arms of the U-shaped holder. Thus, the nozzles are arranged along opposite sides of the wire group in a direction in which the wires are aligned, so that the sealant can be applied simultaneously to the opposite sides of the wire group.
The above-described arrangement of nozzles cannot apply a uniformly thick layer of sealant to both thick wires and thin wires of a wire assembly. More particularly, if the aforementioned constant spacing between the opposed nozzles is set at a value suitable for the thicker wires, then the clearances between the thinner wires and the nozzles are larger than a suitable value. As a result, the sealant must be discharged from the nozzles for a long time to achieve a specified thickness of sealant on the thinner wires. However, this longer application of the sealant causes thicker layers of the sealant on the thicker wires. Conversely, if an attempt is made to achieve a proper application of the sealant to the thicker wires, then the sealant on the thinner wires will not be sufficiently thick. In either case, the thickness of the sealant cannot be uniform on all wires in the assembly produced by the prior art apparatus.
Specifications exist for the thickness of the sealant on wires in a wire assembly, and the specifications vary depending on the type of automotive vehicle. The aforementioned fixed nozzles cannot accommodate the various specifications.
An object of the present invention is to provide a method, which can be carried out when a wire assembly is manufactured, for applying a uniformly thick layer of material to wires in a wire assembly in accordance with the specification of the wire assembly. Another object of the invention is to provide an applicator for this purpose.
The subject invention is directed to a method for applying a material to wires of a wire assembly. The material may be a sealant that has a specified viscosity. The method comprises a first step of aligning wires of a wire group substantially side by side. The method further comprises providing a pair of nozzles for discharging the material. The nozzles are positioned substantially opposed to each other, and the aligned wires are held or positioned the substantially between the opposed nozzles. The method proceeds by moving the nozzles in a wire alignment direction while changing the spacing between the pair of nozzles according to the diameters of the wires so as to cause the material to be applied to and/or to penetrated between the wires.
According to a preferred embodiment, the aligning step comprises aligning the wires according to their diameter, such that the diameters thereof increase in the wire alignment direction.
The moving step may comprise reducing the spacing of the nozzles when the nozzles reach a position along the wire alignment direction corresponding to a clearance between adjacent wires. Alternatively, the discharge of material may be reduced or stopped when the nozzles align with a clearance between adjacent wires.
As a further aspect of the invention, the moving speed of the nozzles along the wire alignment direction may be varied to change the discharge of material onto the wires. Additionally, the rate of discharge of the material may be changed.
The method may be carried out during the manufacturing of a wire assembly, and specifically may be carried out to waterproof a wire assembly that is to be introduced into a grommet. Accordingly, the material applied to the wires may be a sealant that has a specified viscosity. A group of wires of the wire assembly are aligned substantially side-by-side before applying the sealant. The sealant then may be applied by a pair of opposed nozzles disposed on opposite sides of the wire group. The nozzles may be moved in a wire alignment direction, while the spacing between the nozzles is changed according to the diameters of the wires. The application of the sealant is carried out to cause the sealant to penetrate between the wires. A film then is wrapped around a portion of the wire group to which the sealant had been applied, such that the wrapped wire group has a substantially circular cross section. Tape then is applied to at least part of the outer surface of the film.
The above-described movement of the nozzles in the wire alignment direction while causing the nozzles to discharge the sealant, enables the sealant to be applied simultaneously to opposite sides of an area extending over the plurality of wires while penetrating between the wires. This waterproofing treatment is applied during the manufacturing of the wire assembly, and hence the waterproofing process can be simplified and speeded up.
Additionally, the spacing between the pair of nozzles is adjusted according to the diameters of the wires. Consequently, a variation of the clearances between the nozzles and the respective wires when the nozzles are moved in the wire alignment direction can be reduced. As a result, the sealant can be applied uniformly to the entire opposite sides of the wire group in a uniform thickness. Further, wire groups made of wires that have different diameters can be accommodated.
The invention also is directed to an applicator, such as an applicator that can be used in the above described application method. The applicator comprises a pair of nozzles that are substantially opposed to each other on opposite sides of a holder for holding or positioning a wire group. The wire group comprises a plurality of wires that are aligned in a wire alignment direction, such that at least portions of the respective wires are laterally disposed relative to one another. The nozzles are provided for discharging a material, such as a sealant that has a specified viscosity. The applicator further comprises a moving mechanism for moving the pair of nozzles in the wire alignment direction, which is a direction transverse to the individual wires. A feeding mechanism is provided for feeding the material to the nozzles so that a specified amount of the material is discharged from the nozzles. The applicator also comprises a moving means for moving the nozzles toward and away from each other so that the spacing between the pair of nozzles corresponds to the diameter of the wires held between the nozzles.
With this applicator the nozzles are moved in the wire alignment direction while the spacing between the nozzles is changed according to the diameters of the wires. During that time, the specified amount of sealant can be discharged from the nozzles.
The holder preferably is formed such that the wires in the wire group are aligned substantially in the order of their diameters. Wires with the smallest diameters preferably are arranged in a bottommost position as seen in a direction of insertion of the wires into the holder. Additionally, the nozzles are moved while tightly holding the wires in the holder between the nozzles. With this construction, since the nozzles hold the wire group in the holder, the aforementioned spacing with the nozzles and each wire can be minimized easily despite the flexibility of the wires. Thus the sealant applicator can have a simple construction.
Further, since the wires are aligned in the order of their diameters, the nozzles are easily accessible to the respective wires. This is because, if a thinner wire is aligned between thicker wires, it may be difficult for the nozzles to approach this thinner wire. Accordingly, the variation of the above clearance can be reduced, which is preferable to apply the sealant uniformly.
Here, the alignment according to the diameters of the wires includes, for example, an alignment of wires having only slightly different diameters regardless of their diameters in addition to an alignment of wires from the thickest one to the thinnest one.
The nozzles preferably are controlled to stop discharging material at a predetermined timing while the nozzles are moved by the moving mechanism along the wire alignment direction. With this construction, the discharge of the sealant can be stopped if there is a clearance between the aligned wires
The feeding mechanism comprises a source of the material to be applied. The sealant may be a cartridge including a tube that contains the material. An outlet is provided at one end of the tube for discharging the material. A bottom lid is movable inside the tube substantially along the longitudinal direction of the tube. The bottom may be pushed from the other end of the tube to discharge the material. One end of the cartridge can be attached to and removed from a mount portion by moving the cartridge substantially along its longitudinal direction. A pushing bar is provided with an end that can contact the bottom lid of the cartridge attached to the mount portion. A movable member is attachable to and detachable from the other end of the pushing bar and is movable substantially along the longitudinal direction of the cartridge. A permanent magnet may be provided for creating a magnetic attraction that will hold the other end of the pushing bar in or on the movable member.
With this construction, when the cartridge is attached or detached, the movable member is moved away from the mount portion and the pushing bar is detached from the movable member. In this state, the cartridge can be attached or detached easily without interference by the pushing bar.
After the attachment of the cartridge, the movable member holds the pushing bar and is moved toward the mount portion. Then, the bottom lid of the cartridge is pushed by the pushing bar, thereby causing the sealant to discharge through the outlet of the cartridge.
Further, by utilizing the magnetic attraction of the magnet to hold the pushing bar, the pushing bar easily can be attached to and detached from the movable member only by arranging the other end of the pushing bar at the movable member.
These and other objects, features and advantages of the present invention will become apparent upon a reading of the following detailed description and accompanying drawings.